Nuclear particle and radiation detectors. Part 1: Ion chambers and ion-chamber instruments

The paper is a review of the operating mechanisms, special properties and constructional details of the particle and radiation detectors used in modern nuclear instruments. For the most part, the detectors described are those which are in use at the Atomic Energy Research Establishment, at Harwell, and the constructional techniques are those which have been found satisfactory under laboratory conditions there, or under production conditions in British industry. The emphasis in the paper is on the detectors themselves, but brief details are given of their use in complete instruments. The characteristics of the nuclear particles (¿-particles, ß-particles, protons, neutrons, fission fragments, etc.) and quanta (X-rays and ¿-rays) to be detected are discussed, and classification of detectors is given, the principle of detection being explained in each case and attention being called to the two different methods of use, namely as counters responding to each individual ionizing event, and as integrating elements measuring the total energy dissipation over a given interval of time. The paper also gives a detailed description of the ion chamber, the theory of its operation and the practical details of its construction. Examples of its use in radiation monitoring apparatus and in assay instruments are given. Attention is called to the use of ion chambers in process-control instrumentation and in pile-control plants. It is proposed to give a full discussion of proportional counters, Geiger-Mÿller counters and scintillation counters in Part 2 of the paper, to which this part (Part 1) forms an introduction.